1. Field of the Invention
The present invention relates to a thermostatic control device for an air conditioner and more particularly to an intelligent thermostatic control device capable of automatically maintaining a temperature of an air conditioner through a calculation using a comparison between a thermal load estimation and a desired cooling/heating capacity.
2. Description of the Related Art
Each conventional air conditioner has a compressor, a condenser, an expansion valve and an evaporator sequentially connected in series. The condenser has a cooling fan, and the evaporator has a blower. After leaving the compressor, refrigerant inside the air conditioner sequentially passes through the condenser, the expansion valve and the evaporator and returns to the compressor in completion of a cycle of heat absorption and heat dissipation for indoor temperature adjustment. The refrigerant absorbs heat from warm indoor air upon passing through the evaporator, and the heat carried with the refrigerant is blown to an outdoor environment to make the indoor temperature below the outdoor temperature. In the case of a vehicular air conditioner, the compressor of the air vehicular conditioner is driven by the engine. As the revolution per minute (RPM) of the engine fluctuates with the speed of the vehicle as a result of the road condition, the cooling capacity provided by the compressor is also dominated by the vehicle speed. In other words, when the vehicle speed is low, the refrigerant of the air conditioner flows slowly and the temperature inside the vehicle is not cool enough due to a slow cycle of heat absorption and heat dissipation. When the vehicle speed is high, the refrigerant of the air conditioner flows quickly and the temperature inside the vehicle is too cold due to a fast cycle of heat absorption and heat dissipation. Therefore, the uncontrollable temperature issue of the conventional air conditioners causes an unpleasant temperature condition to driver and passengers inside vehicles.
To tackle the issue, the compressor of the foregoing vehicular air conditioner is instead driven by an electric compressor with power supplied from the vehicle itself to keep rotation of the compressor stable and avoid the uncontrollable temperature condition arising from the fluctuating engine speed. However, the compressors of such type of conventional vehicular air conditioners are activated or deactivated through a conventional power on-off control. Suppose that conventional vehicular air conditioners of such type perform a thermostatic cooling operation inside vehicles. Their electric compressors have to be frequently turned on or off according to a temperature set by the air conditioner. Because of the power on-off control, the starting current and the operating power consume more power and overload the power systems of the vehicles, and such thermostatic control is therefore not as satisfactory as expected in terms of performance of air conditioner and energy conservation.